Surgical tourniquet systems of the prior art generally include a pneumatic cuff for encircling a patient's limb at a location proximal to the surgical site, a cuff pressure regulator and a tourniquet controller communicating with a user interface. Surgical tourniquet systems are commonly used to facilitate surgery by stopping the flow of arterial blood into a limb for a period of time sufficient for the performance of a surgical procedure, thereby allowing the surgical procedure to be performed in a dry and bloodless surgical field. Published medical literature indicates that every usage of a surgical tourniquet necessarily causes some injury to the nerve, muscle and soft tissue in the limb beneath the cuff and distal to the cuff. To minimize the nature and extent of such injuries, tourniquet users attempt to minimize the level of cuff pressure employed to establish and maintain a bloodless surgical field distal to the cuff. Also to minimize tourniquet-related injuries, tourniquet operators attempt to minimize the duration of tourniquet cuff pressurization.
A basic prior-art system is described by McEwen in U.S. Pat. No. 4,469,099. If the external AC power supply of McEwen '099 is unexpectedly interrupted while the tourniquet cuff is pressurized, an internal battery continues to provide power to the LED displays and audio alarm but the pressure regulator ceases operation and pneumatic valves in the instrument seal off the pressurized cuff to retain the pressure in the cuff for as long as possible or until external AC power is restored and normal operation can resume. Thus in the event of an interruption of external AC power during use in surgery, McEwen '099 prevents hazards for the patient such as the unanticipated flow of arterial blood into the surgical field during a procedure, the loss of large amounts of blood, and in some cases the loss of intravenous anesthetic agent retained in the limb distal to the cuff.
In U.S. Pat. Nos. 6,213,939 and 6,589,268 McEwen describes apparatus for alerting a user and preventing a hazard arising from the use of prior-art surgical tourniquet systems in which a user could erroneously turn off an electrical power switch of a tourniquet instrument without first deflating the tourniquet cuff. In U.S. Pat. No. 5,855,589 McEwen and Jameson describe additional safety apparatus that helps prevent a hazard in dual-cuff tourniquet systems useful for intravenous regional anesthesia.
Despite many such improvements in the prior art, user errors and malfunctions of tourniquet systems can still be hazardous for patients, especially as design complexity increases and as user interfaces improve. As an example of increasing design complexity, tourniquet apparatus of the prior art described by McEwen and Jameson in U.S. Pat. App. No. 20080262533 is responsive to input signals from remote physiologic monitors tracking a range of physiologic changes of the surgical patient, and can adapt tourniquet cuff pressure in response to a patient's changing limb occlusion pressure. Tourniquet apparatus recently described by McEwen et al. in U.S. patent application Ser. No. 12/389,029 allows a user to test the safety and integrity of tourniquet cuffs prior to use, and further allows the user to increase the cuff pressure beyond a normal maximum safety limit if required to meet the specific needs of a specific patient and surgical procedure. Tourniquet apparatus having wireless sensors and remote user interfaces have also been described in the prior art.
The tourniquet apparatus described by McEwen and Jameson in U.S. Pat. No. 5,607,447 employs a user interface that combines a graphical display and a discrete selector switch for improved display of information and for more intuitive selection and input of actions desired by the user. Replacing this prior-art combination of a discrete selector switch and graphical display with a touchscreen user interface may further improve the display of information and the intuitive selection and input of desired actions. However, employing a touchscreen user interface in a surgical tourniquet system may also be associated with additional hazards arising from user errors and malfunctions.
The present invention suppresses an action initiated by a user of a surgical tourniquet system having a touchscreen user interface if implementation of that action by the system may be hazardous to the surgical patient.